ACCEPTED MANUSCRIPT
mixture was purified by silica-gel flash column chromatography (silica gel, 20 %
EtOAc/Petroleum ether) and recrystallization (CHCl /hexane) yielded purple crystals of 2 (42 mg,
3
1
3
0 % yield). Mp: >300°C. H NMR (400 MHz, CDCl 298K)
δ
= 8.21 (d, J= 8.0 Hz, 2H, Ph), 7.65
3
(
d, J= 16.0 Hz, 2H, vinyl), 7.50 (d, J= 8.0 Hz, 2H, Ph), 8.20 (s, 4H, Ph), 7.24 (d, J= 16.0 Hz, 2H,
vinyl), 6.64 (s, 2H, pyrrole), 5.47 (s, 2H, -OH), 4.01 (s, 3H, -COOCH ), 1.52 (s, 36H, t-Bu), 1.44
3
1
3
(
s, 6H, -Me) ppm; C NMR (100 MHz, CDCl 298K)
δ
= 166.6, 155.8, 153.4, 141.1, 140.5, 137.8,
3
1
36.9, 135.9, 130.6, 130.9, 129.1, 128.2, 124.7, 117.5, 116.8, 52.3, 34.7, 30.5, 14.7 ppm; MS
+
(
MALDI-TOF): Calcd for C H N BF O [M+H] : 815.4771, Found: 815.4773. UV-vis (in
51 62 2 2 4
-1
-1
CH Cl ) λ [nm] (ε [M cm ]): 322 (33,000), 377 (75,100), 603 (48,100), 653 (140,000). Elemental
2
2
Anal. Calc. for C H N BF requires: C, 74.85; H, 4.19; N, 9.70; Found: C, 74.82; H, 4.13; N,
2
7
18
3
2
9
.83.
4
.
Result and discussion
4
.1 Synthesis and characterization
The syntheses of 1 and 2 are shown in Scheme 1. BODIPY derivative 1 was obtained
following a routine formation procedure in a reasonable yield. Then the target probe, 2, was
obtained by condensation reaction of aromatic aldehyde with 1 via a one-pot Knoevenagel
condensation reaction using Dean-Stark apparatus, which, after chromatographic work-up and
recrystallization, was isolated in 30 % yield. The structures of 1 and 2 were characterized by NMR
1
spectroscopy (Fig. S1-S4. in the Supp. Info.). The singlet peaks which lie at 5.47 ppm in the H
NMR spectra of 2 (Fig. S2. in the Supp. Info.), can be assigned to the -OH protons (Fig. S4. in the
Supp. Info.), while the other two singlet peaks lie at 1.51 and 1.44 ppm are assigned to t-Bu- group
and me- group, respectively.
The photophysical properties of 2 are shown in Fig.1 which were measured in THF-H O (v:v
2
=
1:1; HEPES 10 mM, pH= 7.2) solvent under room temperature. The most intense absorption
4
-1
-1
band was found at 653 nm with the molar absorption coefficient (ε) 14.0 × 10 M cm
corresponds to the low energy S0→S1 transition of BODIPY core[17]. The introduction of distyryl
groups to 1 caused large red-shift at about 150 nm of the typical BODIPY absorption band.
Meanwhile the higher energy transitions of the molecular appeared as two weaker bands that
4
-1
-1
around 322 nm and 377 nm with the molar absorption coefficient (ε) 3.3 × 10 M cm and 7.5 ×
4
-1
-1
1
0 M cm , respectively. The absorption spectra of complex 2 was found to be independent in
common organic solvent (Fig. S5. in the Supp. Info.). The emission spectra was also measured
under the same condition for absorption spectra. When excited at 650 nm, 2 exhibited emission
band at 681 nm with the quantum yield of 0.89 indicates that the dye is highly fluorescent. The
Stokes shift is about 28 nm which much more larger that the parent BODIPY 1 [11]. When change
the solvents, the emission spectra were more affected and shown different change tendency while
in n-C H cause blue-shift (664 nm) and in CH OH shown red-shift (689 nm, Fig. S5. in the Supp.
6
14
3
Info.).